U.S. patent number 10,712,063 [Application Number 15/785,614] was granted by the patent office on 2020-07-14 for frozen product dispensing systems and methods.
This patent grant is currently assigned to FBD PARTNERSHIP, LP. The grantee listed for this patent is FBD PARTNERSHIP, LP. Invention is credited to R. Craig Cobabe, Stephen K. Versteeg.
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United States Patent |
10,712,063 |
Cobabe , et al. |
July 14, 2020 |
Frozen product dispensing systems and methods
Abstract
An improved frozen product dispenser wherein a product is placed
into a cooled hopper and the product is then fed from the hopper
into a freezing and dispensing chamber where it is frozen and
dispensed. Applicants have further created improved methods and
apparatuses for to control the refrigeration and freezing systems
of the exemplary frozen product machines are disclosed herein.
Inventors: |
Cobabe; R. Craig (Boerne,
TX), Versteeg; Stephen K. (San Antonio, TX) |
Applicant: |
Name |
City |
State |
Country |
Type |
FBD PARTNERSHIP, LP |
San Antonio |
TX |
US |
|
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Assignee: |
FBD PARTNERSHIP, LP (San
Antonio, TX)
|
Family
ID: |
61902701 |
Appl.
No.: |
15/785,614 |
Filed: |
October 17, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20180106515 A1 |
Apr 19, 2018 |
|
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62409233 |
Oct 17, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A23G
9/281 (20130101); A23G 9/00 (20130101); A23G
9/28 (20130101); A23G 9/22 (20130101); A23G
9/224 (20130101); F25B 41/062 (20130101); A23G
9/228 (20130101); F25B 2600/2513 (20130101); F25B
2600/01 (20130101); F25B 2700/21 (20130101) |
Current International
Class: |
F25B
41/06 (20060101); A23G 9/28 (20060101); A23G
9/22 (20060101); A23G 9/00 (20060101) |
Field of
Search: |
;62/158,222-225 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Russell; Devon
Attorney, Agent or Firm: McAughan Deaver PLLC
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. Provisional patent
application Ser. No. 62/409,233, filed Oct. 17, 2016, the contents
of which are incorporated by reference herein in their entirety.
Claims
What is claimed is:
1. A refrigeration device comprising: (a) a freezing chamber for
freezing a product; (b) an evaporator for cooling the freezing
chamber to a temperature sufficient to permit freezing of the
product; (c) an expansion valve coupled to the evaporator for
regulating the flow of refrigerant through the evaporator; (d) a
sensor for sensing the temperature of the of the refrigerant
flowing through the expansion valve and generating a sensed
temperature signal corresponding to the sensed temperature; (e) a
memory structure including a first set of data defining a first
range of predetermined temperature values and a second set of data
defining a second range of predetermined temperature values wherein
the first range of temperature values is broader than and includes
the second range of temperature values; (f) a controller that
receives the sensed temperature signal from the sensor and controls
the operation of the expansion valve to control the flow of
refrigerant through the evaporator to cool the freezing chamber;
and (g) wherein, during a first time interval, the controller: (i)
controls the operation of the expansion valve at least in part in
response to the sensed temperature signal if the sensed temperature
signal is within the first range of predetermined temperature
values; and (ii) considers as inaccurate any sensed temperature
signal outside the first range; and (h) wherein, during a second
time interval, the controller: (i) controls the operation of the
expansion valve at least in part in response to the sensed
temperature signal if the sensed temperature signal is within the
second range of predetermined temperature values; and (ii)
considers as inaccurate any sensed temperature signal outside the
second range.
2. The refrigeration device of claim 1, wherein the first time
interval begins when the controller begins an operation of the
expansion valve to cool the freezing chamber and ends a
predetermined time period after the beginning of the first time
interval.
3. The refrigeration device of claim 2, wherein the second time
interval begins after the expiration of the first time interval and
ends when the controller ceases operation of the expansion valve to
cool the freezing chamber.
4. The refrigeration device of claim 3, wherein the predetermined
time period is approximately 120 seconds.
5. The refrigeration device of claim 1, wherein the controller
controls operation of the expansion valve by varying a duty cycle
of the expansion valve.
6. The refrigeration device of claim 1, wherein the evaporator has
a high pressure side and a low pressure side and wherein the
temperature sensor senses the temperature of the refrigerant on the
low pressure side of the expansion valve.
7. The refrigeration device of claim 1, wherein the span of
temperatures within the second range is 40% or less of the span of
temperatures within the first range.
8. In a refrigeration device having: a mixing chamber that produces
a product, an evaporator, an expansion valve coupled to the
evaporator for regulating flow of refrigerant through the
evaporator, a temperature sensor for providing a value
representative of a return temperature of the refrigerant, and a
controller that receives the value from the temperature sensor and
regulates a duty cycle of the valve to control the cooling of the
mixing chamber, a method comprising the steps of: (a) initiating
operation of the expansion valve by the controller to cool the
mixing chamber at a first point in time; (b) for a first time
interval following the initiation of the operation of the expansion
valve, considering for control purposes values received from the
temperature sensor that are within a first range of values and
deeming inaccurate and not considering for control purposes values
received from the return refrigerant temperature sensor that are
outside the first range of values; and (c) for a second time
interval following conclusion of the first time interval, deeming
inaccurate and not considering for control purposes values received
from the return refrigerant temperature sensor that are outside a
second range of values, wherein the second range of values is a
subset of the first range of values.
9. The method of claim 8, wherein the first time interval is
approximately 2 minutes.
10. The method of claim 8, wherein the controller controls
operation of the expansion valve by varying the duty cycle of the
expansion valve and wherein the second range of values is
determined, at least in part, based on a duty cycle with which the
controller operates the expansion valve within the second time
interval.
11. The method of claim 8, further comprising the step of not
considering for control purposes during the first time interval any
values received from the temperature sensor after the receipt of a
sensor value outside of the first range of values.
12. The method of claim 8, further comprising the step of
considering for control purposes values received from the
temperature sensor that are within the second range of values,
irrespective of whether any prior received values were outside the
first or second ranges of values.
13. The method of claim 8, wherein the initial operation of the
expansion valve corresponds to initial freezing of the product in
the chamber.
14. The method of claim 8, wherein the initial operation of the
expansion valve corresponds to a refreezing of the product in the
chamber.
15. In a refrigeration device having: a mixing chamber that
produces a product, an evaporator, an expansion valve coupled to
the evaporator for regulating the flow of refrigerant through the
evaporator, a temperature sensor for providing a value
representative of a return temperature of the refrigerant, and a
controller that receives values from the temperature sensor and
regulates the duty cycle of the valve to control the cooling of the
mixing chamber, a method comprising the steps of: (a) initiating
operation of the expansion valve by the controller to cool the
mixing chamber at a first point in time; (b) for a first time
interval following the initiation of the operation of the expansion
valve, controlling the duty cycle of the expansion valve and
considering for control purposes values received from the
temperature sensor that are within a first range of values at least
partially determined by the duty cycle at which the expansion valve
is being operated at the time the sensor value is received and not
considering for control purposes values received from the return
refrigerant temperature sensor that are outside the first range of
values; (c) for a second time interval following the conclusion of
the first time interval, considering for control purposes values
received from the temperature sensor that are within a second range
of values, at least partially determined by the duty cycle at which
the expansion valve is being operated at the time the sensor value
is received, and not considering for control purposes values
received from the return refrigerant temperature sensor that are
outside the second range of values, wherein the second range of
values is a subset of the first range of values.
16. The method of claim 15, wherein the first time interval is
approximately 2 minutes.
17. The method of claim 15, further comprising the step of not
considering for control purposes any values received from the
temperature sensor after the receipt of a sensor value outside of
the first range of values during the first time interval.
18. The method of claim 15, wherein the initial operation of the
expansion valve corresponds to the initial freezing of the product
in the chamber.
19. The method of claim 15, wherein the initial operation of the
expansion valve corresponds to a refreeze of the product in the
chamber.
Description
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH/DEVELOPMENT
Not applicable.
REFERENCE TO APPENDIX
Not applicable.
BACKGROUND OF THE INVENTION
The subject matter of this disclosure relates to improved frozen
product dispenser systems and methods wherein a product is placed
into a cooled hopper and the product is then fed from the hopper
into a freezing and dispensing chamber where it is frozen and
dispensed. More specifically, the subject matter of this disclosure
is related to improved systems and methods of controlling the
refrigeration and freezing of product of a frozen product
dispenser.
Frozen product dispensers, generally, have been known in the art
and have been used to freeze and dispense a variety of products
including, but not limited to food products such as beverages, ice
cream, yogurt, and other food items. Such prior art dispensers have
suffered from various shortcomings and/or limitations.
The temperature and viscosity of the ingredients within the mixing
chamber may be maintained by a control system that controls the
refrigeration system. A method for controlling a frozen beverage
machine's barrel refreeze cycle is based on the beater motor's
torque (or power consumption). When the measured torque on the
beater motor drops below a specified threshold, the machine
initiates a freeze cycle and chills the barrel until the torque on
the motor reaches a higher specified torque. While this is an
indicator of the quality of the frozen product, other sensors
throughout the dispensing device may be used to ensure that all of
the functions work properly and that the motor torque reading is
not providing an erroneous value.
In normal operation, a mix of ingredients are poured into a hopper,
and some portion of that mix is allowed to flow downward into the
freezing chamber. A motor outside of the freezing chamber drives a
beater, which mixes the mix with air. Simultaneously a
refrigeration unit chills the mix in the freezing barrel rapidly
cooling it to the desired temperature.
Over time, the freezing barrel will lose heat through entropy and
the freezing cycle will need to be repeated. Also, product will be
dispensed and new mix added which will be at a temperature higher
than the product in the freezing chamber. Since the goal of a
frozen food dispenser is to provide uniform and quality product,
the freezing cycle must be carefully regulated to ensure that the
product does not deviate too far from optimal conditions.
To address this goal of providing consistent and quality product,
several processes are loaded into the controller of the dispensing
unit, and in fact, multiple controllers may be designed into the
unit to guard against the failure of the primary controller. The
controller may be a PID (proportional-integral-derivative)
controller, a microprocessor, or similar electronic control
apparatus. The main control process will bring the mix to a desired
product using all sensors available to it under normal
circumstances. While the units are built with the highest
achievable quality standards, components such as sensors are known
to fail, or to be jarred loose from their designed positions
resulting in erroneous readings being fed into the control
processor. Since relying upon those erroneous readings may provide
undesirable product, the readings received by the control processor
are checked against expected norms. If a sensor is providing
readings that are outside of expected norms, the controller may
distrust the reading and implement an alternate control program in
an attempt to continue to provide desirable product. In creating
the programming for the controllers, two objectives come to the
forefront: (i) ensure that the tolerances around the expected
sensor readings are not too wide to accept skewed readings but yet
not too tight to reject correct readings and (ii) implement
alternative control programs that will continue to provide quality
product ready for dispensing even under rather adverse conditions
resulting from the loss of inputs and feedbacks.
Under adverse conditions, the logic that will be used in exemplary
dispensing systems must rely upon input and feedback from
components that normally do not provide the primary inputs for the
process. As such, the logic must be flexible and anticipate
conditions that may prevent it from providing a quality food
product.
One of several objects of the teachings of this disclosure is to
resolve or reduce the identified--and other--shortcomings and/or
limitations in prior art frozen product dispensers.
BRIEF SUMMARY OF SELECT ASPECTS OF THE INVENTION
None of these brief summaries of the aspects invention is intended
to limit or otherwise affect the scope of the appended claims, and
nothing stated in this Brief Summary of the Invention is intended
as a definition of a claim term or phrase or as a disavowal or
disclaimer of claim scope.
In one of many summaries of the inventions disclosed herein is a
refrigeration device comprising: (a) a freezing chamber for
freezing a product; (b) an evaporator for cooling the freezing
chamber to a temperature sufficient to permit freezing of the
product; (c) an expansion valve coupled to the evaporator for
regulating the flow of refrigerant through the evaporator; (d) a
sensor for sensing the temperature of the of the refrigerant
flowing through the expansion valve and generating a sensed
temperature signal corresponding to the sensed temperature; (e) a
memory structure including a first set of data defining a first
range of predetermined temperature values and a second set of data
defining a second range of predetermined temperature values wherein
the first range of sensor values is broader than and includes the
second range of sensor values; (f) a controller that receives the
sensed temperature signal from the sensor and controls the
operation of the expansion valve to control the flow of refrigerant
through the evaporator to cool the freezing chamber; and (g)
wherein, during a first time interval, the controller: (i) controls
the operation of the expansion valve at least in part in response
to the sensed temperature signal if the sensed temperature signal
is within the first range of predetermined temperature values; and
(ii) considers as inaccurate any sensed temperature signal outside
the first range; and (h) wherein, during a second time interval,
the controller: (i) controls the operation of the expansion valve
at least in part in response to the sensed temperature signal if
the sensed temperature signal is within the second range of
predetermined temperature values; and (ii) considers as inaccurate
any sensed temperature signal outside the second range.
Yet another summary of the inventions disclosed herein is a
refrigeration device having: a mixing chamber that produces a
product, an evaporator, an expansion valve coupled to the
evaporator for regulating the flow of refrigerant through the
evaporator, a temperature sensor for providing a value
representative of the return temperature of the refrigerant, and a
controller that receives the value from the temperature sensor and
regulates the duty cycle of the valve to control the cooling of the
mixing chamber, a method comprising the steps of: (a) initiating
operation of the control valve by the controller to cool the mixing
chamber at a first point in time; (b) for a first time interval
following the initiation of the operation of the control valve,
considering for control purposes values received from the
temperature sensor that are within a first range of values and
deeming inaccurate, and not considering for control purposes values
received from the return refrigerant temperature sensor that are
outside the first range of values; (c) for a second time interval
following the conclusion of the first time interval, deeming
inaccurate and not considering for control purposes values received
from the return refrigerant temperature sensor that are outside a
second range of values, wherein the second range of values is a
subset of the first range of values.
The following examples are included to demonstrate preferred
embodiments of the inventions. It should be appreciated by those of
skill in the art that the techniques disclosed in the examples,
which follow represent techniques discovered by the inventors to
function well in the practice of the inventions, and thus can be
considered to constitute preferred modes for its practice. However,
those of skill in the art should, in light of the present
disclosure, appreciate that many changes can be made in the
specific embodiments which are disclosed and still obtain a like or
similar result without departing from the scope of the
inventions.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
The following figures form part of the present specification and
are included to further demonstrate certain aspects of the present
invention. The invention may be better understood by reference to
one or more of these figures in combination with the detailed
description of specific embodiments presented herein.
FIGS. 1A-1C illustrate at a high level an exemplary frozen product
dispenser constructed in accordance with certain teachings set
forth herein.
FIG. 2 illustrates certain details an exemplary frozen product
dispenser in which the hopper is positioned above the mixing and
freezing barrel in accordance with certain teachings set forth
herein.
FIG. 3 illustrates an isometric cross-sectional view of exemplary
frozen product dispenser showing a single hopper, a freezing and
mixing barrel, a separation plate, and a mixing tube of an in
accordance with certain teachings set forth herein.
FIG. 4 is a schematic diagram of a frozen beverage machine in
accordance with certain teachings of the present disclosure.
FIG. 5 is a block diagram conceptually illustrating a refrigeration
system of a frozen beverage machine in accordance with certain
teachings of the present disclosure.
FIG. 6 illustrates a chart of various data collected from sensors
during the freeze cycle of an exemplary dispensing system in
accordance with certain teachings of the present disclosure.
FIG. 7 illustrates a chart showing how the duty cycles of the
refrigeration unit expansion valve of thirty-one freezes are
plotted against the return temperature of the refrigerant in
accordance with certain teachings of the present disclosure.
FIG. 8 is a plot showing a subset of the same data from only using
the duty cycle compared to the refrigerant return temperature after
two minutes had elapsed from the start of the first freeze
cycle
FIG. 9 is a flow diagram illustrating an exemplary refrigeration
temperature sensor offset detection logic of a frozen beverage
machine in accordance with certain teachings of the present
disclosure.
FIG. 10 illustrates a control block diagram of an exemplary method
of duty cycle hysteresis gain scheduling in accordance with certain
teachings of the present disclosure.
FIG. 11 illustrates an example of the block diagram of an exemplary
method of duty cycle hysteresis gain scheduling in accordance with
certain teachings of the present disclosure.
FIG. 12 illustrates a block diagram of beater load rate controller
in accordance with certain teachings of the present disclosure.
FIG. 13 illustrates an example of a fuzzy rule set in accordance
with certain teachings of the present disclosure.
FIG. 14 illustrates a block diagram of another exemplary method of
fuzzy logic in accordance with certain teachings of the present
disclosure.
FIG. 15 illustrates a control block diagram of an exemplary method
of cascaded PID Control using superheat in accordance with certain
teachings of the present disclosure.
FIG. 16 illustrates a control block diagram of an exemplary method
of cascaded PID Control using low side pressure in accordance with
certain teachings of the present disclosure.
FIG. 17 illustrates a chart of various data collected from sensors
during the freeze cycle of an exemplary dispensing system in
accordance with certain teachings of the present disclosure.
While the inventions disclosed herein are susceptible to various
modifications and alternative forms, only a few specific
embodiments have been shown by way of example in the drawings and
are described in detail below. The figures and detailed
descriptions of these specific embodiments are not intended to
limit the breadth or scope of the inventive concepts or the
appended claims in any manner. Rather, the figures and detailed
written descriptions are provided to illustrate the inventive
concepts to a person of ordinary skill in the art and to enable
such person to make and use the inventive concepts.
DETAILED DESCRIPTION
The Figures described above and the written description of specific
structures and functions below are not presented to limit the scope
of what Applicants have invented or the scope of the appended
claims. Rather, the Figures and written description are provided to
teach any person skilled in the art to make and use the inventions
for which patent protection is sought. Those skilled in the art
will appreciate that not all features of a commercial embodiment of
the inventions are described or shown for the sake of clarity and
understanding. Persons of skill in this art will also appreciate
that the development of an actual commercial embodiment
incorporating aspects of the present inventions will require
numerous implementation-specific decisions to achieve the
developer's ultimate goal for the commercial embodiment. Such
implementation-specific decisions may include, and likely are not
limited to, compliance with system-related, business-related,
government-related and other constraints, which may vary by
specific implementation, location and from time to time. While a
developer's efforts might be complex and time-consuming in an
absolute sense, such efforts would be, nevertheless, a routine
undertaking for those of skill in this art having benefit of this
disclosure. It must be understood that the inventions disclosed and
taught herein are susceptible to numerous and various modifications
and alternative forms. Lastly, the use of a singular term, such as,
but not limited to, "a," is not intended as limiting of the number
of items. Also, the use of relational terms, such as, but not
limited to, "top," "bottom," "left," "right," "upper," "lower,"
"down," "up," "side," and the like are used in the written
description for clarity in specific reference to the Figures and
are not intended to limit the scope of the invention or the
appended claims.
Particular embodiments of the invention may be described below with
reference to block diagrams and/or operational illustrations of
methods. It will be understood that each block of the block
diagrams and/or operational illustrations, and combinations of
blocks in the block diagrams and/or operational illustrations, can
be implemented by analog and/or digital hardware, and/or computer
program instructions. Such computer program instructions may be
provided to a processor of a general-purpose computer, special
purpose computer, ASIC, and/or other programmable data processing
systems. The executed instructions may create structures and
functions for implementing the actions specified in the block
diagrams and/or operational illustrations. In some alternate
implementations, the functions/actions/structures noted in the
figures may occur out of the order noted in the block diagrams
and/or operational illustrations. For example, two operations shown
as occurring in succession, in fact, may be executed substantially
concurrently or the operations may be executed in the reverse
order, depending upon the functionality/acts/structure
involved.
Turning to the drawings and, in particular, to FIGS. 1A, 1B, and 1C
aspects of an exemplary frozen product dispenser 100 are
illustrated. For purposes of the following discussion, the product
to be dispensed by the frozen product dispenser 100 will be
described in the context of a dairy-based food product, such as a
soft serve ice cream product, smoothies, milk shakes, or a frozen
yogurt product. It should be understood, however that--unless
explicitly so indicated--the teachings, disclosure and recitation
of claimed subject matter set forth herein is not limited to food
products generally, or to dairy-based food products specifically,
and that the teachings and disclosed embodiments discussed herein
may be beneficially used in connection with other food products and
with non-food products. For example, the teachings, disclosure and
recitation of claimed subject matter set forth herein may be
applicable for example to soft serve, frozen yogurt, milkshake,
smoothies, beverage, and frozen beverages, as well as to carbonated
drinks, and many other types of food and non-food products.
Components and arrangements suitable for use as the main system
structure 1000 are illustrated, for example, in issued U.S. Pat.
Nos. 6,536,224, 6,625,993, 8,528,786, 8,701,939, 8,875,732, and
9,388,033, and in Published Pending U.S. Patent Application Nos.
20100293965 and 20160089702, the relevant disclosure of which are
incorporated herein by reference in its entirety. For purposes of
easy discussion, at a high level, the illustrated frozen product
dispenser 1000 may be considered as including four basic
operational systems.
Initially, the illustrated frozen product dispenser 100 includes a
product storage system that includes basins in the form of hoppers
101 and 102 that are designed to receive and store the product to
be frozen and dispensed. Access to the hoppers 101 and 102 may be
provided via removable lids 103 and 104 and product to be frozen
and dispensed may be poured into the hoppers 101 and 102. As
described in the illustrated exemplary system, the product storage
system may include components to (i) quickly bring the product in
the hoppers 101 and 102 to a desired temperature, (ii) to maintain
the product in the hoppers at a desired temperature and (iii) to
control the flow of heat into and from the contents of the hopper
so as to subject the contents to various processes--such as a
pasteurization process. In addition, the product storage system may
include sensors and systems for detecting, directly and/or
inferentially, the level of product in the hoppers 101 and 102 to
alert the operator of the frozen product dispenser when the
contents are low and/or in a condition wherein dispensing should be
halted. The product storage system includes fill tube
assembly/mix-tubes 232 to deliver the product from the hoppers 101,
102 to the freezing barrels 105, 106.
In addition to the product storage system, the illustrated frozen
beverage dispenser further includes a product freezing system that
includes one or more freezing barrels 105 and 106 that receive
product from the hoppers 101 and 102 and freeze the product for
subsequent dispensing. In the illustrated embodiment, the product
freezing system also includes a rotating scraper or beater
positioned inside the freezing barrels (not specifically
illustrated in FIGS. 1A-1C) that are driven, in a controlled
manner, by drive motors (one of which 120 is illustrated in FIGS.
1B and 1C). Additional details of the product freezing system are
provided below.
The illustrated frozen product dispenser 100 further includes a
refrigeration system that includes a compressor 130 and a condenser
132. In operation, the refrigeration system provides compressed
refrigerant to the evaporators within the product storage system
and the product freezing system to cool the stored product and/or
freeze the product in the freezing system, and receives vapor from
the evaporators that is then compressed, passed through the
condenser, and provided to the product and storage systems to
repeat the refrigeration cycle.
Further, the illustrated frozen product dispenser includes a
dispensing and interface system that includes dispensing valves 140
and 141 and a control and man-machine interface 150. As described
in more detail below, the dispensing valves 140 and 141 may be
actuated to dispense frozen product from the freezing barrels
and/or locked out to prevent the dispensing of product. The
man-machine interface 150 may be used to permit configuration of
the frozen product dispenser 100 and/or the input of data that can
be used to control the operation of the dispenser. It can also be
used to provide notices and information from the dispenser to the
operator of the frozen product dispenser.
It will be appreciated that the four systems described above are
not necessarily isolated from each other and that the placement of
a specific physical component within one system is, to some extent,
arbitrary. For example, the evaporators used to cool the contents
of the hoppers 101 and 102 could almost equally be considered part
of the product storage system or the refrigeration system. The
references to the various systems contained herein should,
therefore, not to be considered physical aspects of the described
frozen product dispenser 100, but rather concepts useful in
describing various aspects of the structure and operation of the
exemplary systems, methods and apparatus discussed herein.
As reflected most specifically in FIG. 1C the frozen product
dispenser also includes various support and shrouding elements that
are not specifically numbered or discussed but will be understood
to form part of the dispenser structure.
Certain details of the product storage system are generally
provided in FIG. 2.
FIG. 2 illustrates certain details an exemplary frozen product
dispenser in which the hopper is positioned above the mixing and
freezing barrel in accordance with certain teachings set forth
herein. As reflected in FIG. 2, the exemplary product storage
system includes hoppers 101 and 102, which, in the illustrated
example, are in the form of stainless steel basins. Freezing
barrels 105 and 106 are located below hoppers 101 and 102 allowing
gravity to draw product from the hoppers 101 and 102 into the
freezing barrels 105 and 106. An opening in each hopper is provided
to receive a single sensor 170 and 180. The sensors 170 and 180 may
take various forms and can be capacitance sensors, resistive
sensors, infrared sensors, acoustic sensors, mechanical float
sensors or any other suitable sensors. In the illustrated example,
the sensors 107 and 108 are conductive sensors whose output varies
between two states, one corresponding to a situation where the
sensor is covered with product in the hopper, and the other where
the level of product in the hopper has dropped to a level such that
the sensor is no longer covered with the product to be
dispensed.
FIG. 3 illustrates an isometric cross-sectional view of exemplary
frozen product dispenser showing a single hopper, a freezing and
mixing barrel, a separation plate, and a mixing tube in accordance
with certain teachings set forth herein. As reflected in FIG. 3,
hopper 300 is formed to provide a low point 305 and a funnel-like
structure that narrows towards the low point. An opening is
provided at the low point of hopper 301 to facilitate the flow of
the product. This design thus results in gravity feeding product
placed into the hopper 301 to, and through the openings at the low
points, thus allowing the gravity-fed filling of product from the
hopper 301.
FIG. 4 is a schematic diagram of a frozen beverage machine in
accordance with certain teachings of the present disclosure. FIG. 4
is a simplified block diagram schematically illustrating components
of a frozen beverage machine 10 in accordance with certain
teachings of or could be used in conjunction with the present
disclosure. In FIG. 4, the frozen beverage machine 10 is an
exemplary frozen beverage machine constructed in accordance with
certain teachings set forth herein. The frozen beverage machine 10
includes an ingredients supply source 12, a process flow block 14,
a controller 16, and a product freezing chamber or barrel 18. In
the exemplary frozen beverage machine 10, the ingredient supply
source 12 may include, for example, a water supply, syrup supply
and a gas supply, or alternatively it may contain a dairy mix In
the illustrated embodiment, the barrel 18 comprises a freezing
chamber having a refrigeration system 20 associated therewith. The
barrel 18 further comprises a beater 24. The product chamber or
barrel 18 may comprise an evaporator in the refrigeration system
20. The frozen beverage machine 10 may alternatively have one or
more barrels. Further descriptions of frozen beverage machines are
provided in U.S. Pat. Nos. 5,706,661; 5,743,097; 5,799,726;
5,806,550; 6,536,224 and 6,625,993 by J. I. Frank, et al. The
entire disclosures of these patents are incorporated by reference.
Other known frozen beverage machines may be used in conjunction
with methods and apparatuses disclosed in the present
disclosure.
The chamber or barrel 18 is where product or liquid is frozen and
maintained before dispensing. Initial pull down (IPD) is a process
of freezing a liquid in the barrel 18 from a liquid state to a
frozen ready to serve state. This occurs when barrel is initially
filled with liquid ingredients and the refrigeration system is
cooling the freezing barrel 18. The thaw period or thaw cycle
occurs when one of the barrels 18 of the frozen beverage machine 10
is turned on, but the refrigeration system 20 is off. The product
or liquid in the barrel 18 is frozen and ready to serve, but is
naturally thawing and not being frozen by the refrigeration system
20. The initial pull down freeze cycle or refreeze cycle occurs
when one of the barrels 18 of the frozen beverage machine 10 is
turned on and the refrigeration system 20 is on. A freeze cycle
occurs between thaw cycles.
Beater percentage (represented as Btr %) is a measure, found by
Applicants, of the torque load on the motor and is generally
inversely proportional to the motor load. As such, Applicants have
found that the Btr % value drops when the load on the drive motor
increases. Applicants have defined that 1000% be used when the
barrel is filled with a non-frozen liquid. Frozen liquids have
lower values, down to 0% where the motor cannot turn the
beater.
The level of the ingredients for a frozen beverage mixture are
provided from the ingredient supply 12 to the process flow block
14, which controls the flow of the ingredients into the freezing
chamber 18 as directed by the controller 16. The controller 16 may
comprise an appropriately programmed microprocessor, suitable
memory and input devices, and suitable controls. The frozen mixture
consistency is controlled by any of a number of methods that turns
on the refrigeration system 20 to freeze and turns off the
refrigeration system 20 when the mixture reaches the desired
consistency. Suitable operation of the controller 16 and other
control instrumentation using circuit boards, volatile and
non-volatile memory devices, software, firmware, and the like is
described, for example, in U.S. Pat. No. 5,706,661 incorporated by
reference above. The product is then dispensed through a dispensing
valve 22.
FIG. 5 illustrates a block diagram conceptually illustrating a
refrigeration system of a frozen beverage machine in accordance
with certain teachings of the present disclosure. The refrigeration
system includes a compressor 54, a heat exchanger 56, a condenser
58, and a pair of evaporators 60 and 62, as shown in FIG. 5. In
another embodiment, the heat exchanger 56 may be a unit comprising
a heat exchanger and accumulator. The heat exchanger 56 is
connected by a line 64 to pulse modulated expansion valves 66 and
68, which control delivery of the condensed refrigerant to the
evaporators 60 and 62, respectively, which envelope mixing chambers
40 and 42. In an alternate design, the pulse modulated expansion
valves 66 and 68 may be substituted by other types of thermal
expansion valves. The evaporators 60 and 62 are each defined by a
sleeve having an advancing helical groove formed along its inner
circumferential surface. The evaporators 60 and 62 are preferably
shrink fitted onto the outer surfaces of mixing chambers 40 and 42,
respectively. The helical grooves define flow paths 70 and 72,
which encircle the mixing chambers 40 and 42, respectively. The
refrigerant flows through the flow paths 70 and 72 so as to come
into direct contact with the walls of the mixing chambers 40 and
42, respectively. This provides for efficient heat transfer. The
flow paths 70 and 72 empty into a common outlet 74 which, in turn,
is connected to the heat exchanger 56 by line 76.
The heat exchanger 56 delivers the expanded refrigerant to the
compressor 54 via line 77. The compressor 54 delivers the
refrigerant to the condenser 58 via line 78. The condenser 58, in
turn, delivers the refrigerant to the accumulator 56 via line 80.
The operation of the various components of the refrigeration system
is well known in the art, and therefore will not be further
discussed herein.
It should be understood, however that--unless explicitly so
indicated--the teachings, disclosure and recitation of
refrigeration systems set forth herein is not limited to this
embodiment specifically. The operation of the various components of
the refrigeration system is well known in the art and may be used
in combination with or in replacement of this particular
embodiment.
Applicants have further created improved methods and apparatuses to
control the refrigeration and freezing systems of exemplary frozen
product machines disclosed herein.
Applicants have further created improved methods and apparatuses
for refrigeration temperature sensor offset detection. The
exemplary refrigeration temperature sensor offset detection is a
method of early detection of an offset of a temperature sensor
being used for feedback as part of a refrigeration system of a
frozen beverage dispenser. The outcome of this detection is not a
precise offset measurement but rather if the offset is significant
enough to not be within certain desirable parameters for the
refrigeration system of the frozen product dispenser, and thusly
used as the input to refrigeration control algorithms, it may be
discarded. This has an advantage over testing the sensor input
against its defined range, as this method cannot detect an offset.
As an example, a significant offset in the return temperature being
used to calculate superheat as input to a superheat refrigeration
controller can render the controller completely ineffective. This
can lead to a frozen beverage dispenser being completely
inoperable. Once the input--which has been determined to not be
within desirable parameters--is discarded, other control methods
that can be effective without the temperature sensor may be
used.
The methods Applicants have created offer more robust refrigeration
control by early detection of bad sensory input from the
evaporator's return temperature sensor. Historically used methods
to determine the validity of a temperature sensor input involves
testing its input against the entire accepted operating range of
that sensor. For example, if the operating range of the sensor and
analog measurement circuitry for a temperature sensor is from
-40.degree. F. to 90.degree. F. (-40.degree. C. to 32.2.degree.
C.), a temperature reading is said to be valid as long as it falls
within this range. In extreme cases, such as a circuit fault
resulting in the sensor not being connected, or a short circuited
sensor, or any number of other problems, the temperature reading
will fall outside the valid range and be noted as invalid. It
should not then be considered for input into refrigeration control
methods.
For example, in cases where the temperature reading is offset by
some amount such as +30.degree. F. (an offset of +16.7.degree. C.),
a reading of 0.degree. F. (-17.8.degree. C.) will read as a
30.degree. F. (-1.1.degree. C.). This increases the superheat
reading by that offset, for which a superheat refrigeration
controller, for instance, will try to compensate by reducing the
superheat. Previous methods for checking the validity of a
temperature input will not be able to detect this condition. The
30.degree. F. (+16.7.degree. C.) offset falls within the acceptable
range and therefore may appear reasonable. But as described in the
last paragraph, this is not acceptable.
The methods and inventions disclosed herein may use a more precise
range by checking the evaporator's return temp sensor under known
conditions and assumptions.
FIG. 6 illustrates a chart of various data collected from sensors
during the initial cooling cycle of an exemplary dispensing system
in accordance with certain teachings of the present
disclosure--more particularly an example of a the initial cooling
cycle of a shakes and smoothies dispenser. It demonstrates a
settling period followed by a stable period in which the return
temperature drops slowly as the product freezes down. This graph
represents a refreeze over time wherein the mix has been frozen,
has thawed and the mechanisms are activated to chill it. The "Btr
%" line represents a parameter that is inversely correlated to the
viscosity of the product in the freezing barrel and is measured
from the torque imparted to the beater motor from the product in
the freezing chamber. A value of 0% represents a solid that the
beater cannot push against and a value of 1000% represents a fluid
with a consistency near that of water. This value is applicable to
all frozen beverage machines regardless of their size or other
operating parameters, which may differ. Therefore finding a desired
quality of a product to be dispensed in one type of frozen
dispenser may be quantified and applied to all other dispensers.
This curve shows that the mix added to the chamber has a low Btr %
value but is beaten to add air, expanding the mix and raising the
Btr % value. The product "settles" while it cools producing a
desirable consumable when the slope of the line flattens and
remains constant. During this time, the superheat initially raises
but then gradually settles as the product in the freezing barrel
cools.
A first consideration of the controller is to ascertain that the
data being received is valid. If a temperature sensor is rated to
be reliable between a broad range then the controller may be
initially programmed to accept any value within that range as
valid. However, if the temperatures that it is going to measure are
known to be within a much narrower range, then the controller
should be programmed to only accept temperatures within that range
as valid.
FIG. 6 represents a single refreeze; however the data from 31
refreezes was analyzed to determine the appropriate expected range
and conditions and is shown in FIG. 7.
FIG. 7 is a plot showing the duty cycles of the refrigeration unit
expansion valve of thirty-one freezes. The duty cycles of these
freezes are plotted against the return temperature of the
refrigerant. There are several datum of when the duty cycle was 40
and in each case the refrigerant return temperature was between
0.degree. F. and -20.degree. F. (-17.8.degree. C. to -28.9.degree.
C.). At the other end, there are many datum where the duty cycle
was 80 and the refrigerant return temperature was between
20.degree. F. and 80.degree. F. (-6.7.degree. C. to 26.7.degree.
C.). From this, it may be determined that the valid range of the
refrigerant return temperature be between -20.degree. F. and
80.degree. F. (-28.9.degree. C. to 26.7.degree. C.).
FIG. 8 is plot showing a subset of the same data from only using
the duty cycle compared to the refrigerant return temperature after
two minutes had elapsed from the start of the first freeze cycle.
This indicates that a far narrower range of temperatures may be
selected to determine if a temperature sensor reading is valid. At
first glance, the range of valid readings could be set as between
-20.degree. F. and +20.degree. F. (-28.9.degree. F. to -6.7.degree.
C.). However, since the data are linearly aligned, further narrower
ranges may be imposed relative to the duty cycle. For instance, a
range of between -20.degree. F. and +10.degree. F. (-28.9.degree.
C. to -12.2.degree. C.) may be imposed for when the duty cycle is
between 40 and 60, and a range between 0.degree. F. and 20.degree.
F. (-17.8.degree. C. to -6.7.degree. C.) may be imposed between
duty cycles 60 to 80. Those skilled in the art will be able to
segment these ranges by duty cycles as appropriate and will know
what additional margin of safety will need to be added to each
range for proper operation.
It is acknowledged that there is a risk that the temperature sensor
may fall out of this range but also be valid. This could occur in
instances where the refrigeration charge is out of specification,
or the condenser fan is inoperable, or the airflow to the unit is
blocked, or any other source that may cause the refrigeration
system to be ineffective. This method alone cannot distinguish
between an invalid sensor condition and these other instances.
However, the result in these cases is that the frozen beverage
dispenser will continue to attempt to freeze using other control
methods that may be slightly less effective, but will still
dispense a product satisfying to a consumer. Furthermore, the fact
remains that there is an error condition that needs to be resolved
and troubleshooting of this error condition should include
validating that the temperature sensor is indeed bad and ruling out
other causes.
FIG. 9 is a flow diagram illustrating an exemplary refrigeration
temperature sensor offset detection logic of a frozen beverage
machine in accordance with certain teachings of the present
disclosure. A decision point for moving from the broad range of
valid temperature sensor values to a narrow one is represented as a
time after the initial pull down has started. One of ordinary skill
in this art will recognize that other metrics may be used rather
than a simple timer. Also, those skilled in the art will recognize
that a logic path such as described in FIG. 4 may be applied to any
sensor input, even those other than temperature sensor values.
FIG. 9 may be described as a routine contained within the overall
control process. The process 900 may be first invoked when the
exemplary frozen product dispenser is first started. The process
900 may then be invoked at any time, and as often as the validity
of the inputs needs to be validated thereafter. This may be done at
the receipt of each new input value, or delayed until some number
of inputs have been received, or delayed until some amount of time
has passed since it was performed before. Invoking this subroutine
starts with initiating the run sequence 902. When this routine
starts, the input from the temperature sensor will be received 904
and will be indexed with the corresponding duty cycle of the PWM
valve. Next, the initial temperature range for each PWM valve duty
cycle will be assigned 906 consisting of a broad range of values.
As was noted earlier, this temporary range will be broad enough and
contain enough of a margin of safety to cover the startup process
where the readings are expected to vary widely for each
corresponding duty cycle. A comparison 910 will be made between the
temperature reading received and the assigned temperature range
where both are indexed to the duty cycle. If the received
temperature reading is not within the assigned initial temperature
range then the controller will not use the received temperature
reading 912 and will control the freezing/heating cycle without
this input. However, if the received temperature reading is within
the initial temperature range assigned then it may be used as input
to control the freezing/heating cycle of the overall control
process. Processing continues by making another decision 914 to
determine if the initial freeze down timer has expired. As noted
earlier, this may be 2 minutes during a refreeze cycle. If that
timer has not expired, the temporary initial temperature range,
assigned in 906, will continue to be used to compare new
temperature readings received. However, if the timer has expired,
the tighter valid temperature range, indexed to the duty cycle,
will be used 908 as the comparator in making a validity decision
910.
Applicants have found that while accurate measure have been found
using a time period of 2 minutes for a refreeze cycle, more
accurate measures have been found using a time period of 4 minutes.
Similar measures were obtained for measures during an initial
freeze where the contents in the freezing barrel are still liquid
and have not been frozen. In that case, an initial time period of
20 minutes has been found to provide accurate measures.
Another exemplary embodiment of this invention may be that the
process may continue even after the decision has been made to not
use the readings from the temperature sensor because it is outside
the accepted range for that duty cycle. In this case, the readings
may continue to be received and compared to the assigned valid
range but not used to control the freezing/heating cycle unless the
readings start falling within the accepted valid range indexed to
the duty cycle. This may happen if an operator or technician
notices that a sensor has fallen away from where it is supposed to
be and appropriately reattaches it. In that case, extra steps may
be taken to validate the temperature readings against other known
inputs received during normal operations.
Applicants have further created improved methods and apparatuses
for controlling the refrigeration by using the beater load rate of
change in non-linear manner. This exemplary control method may be
used as a backup control method to control methods using superheat
and pressure measures, or may be used as a standalone method. Its
advantages include that it does not require temperature or pressure
measures for feedback. Moreover, it may more directly influence the
speed of the freeze than other known control methods.
One prior art method of making decisions for controlling the
refrigeration system has been to monitor the beater load and
compare its measures to a table. If the beater load was not at a
predicted point along a line representing a freeze, then the duty
cycle of the refrigeration system could be adjusted to either
freeze faster or slower. This method may not respond appropriately
to several conditions, and may cause the system to become unstable
as it attempts to refrigerate using this rote method.
The inventions disclosed herein may use indirect feedback
information to make adjustments to the duty cycle of the
refrigeration system. In one embodiment, the change in the rate of
the beater load has been found to be an effective method for
controlling the duty cycle of the refrigerant system. Applicants
have found that by using this method, the refrigeration system may
be effectively controlled without the use of direct feedback
methods of parameters such as suction pressure or return
temperature. This allows the system to continue operations even
when some sensors normally used in the system become
inoperative.
In one exemplary method of using indirect feedback to control the
system, Applicants have found that the rate of change of the beater
load may be used as an input to the controller. This may be seen in
the following formula. Input=(BTR % [n]-BTR % [n-j])/j n=current
sample j=previous sample index (10 was used)
In this, the values for BTR % at a number of times may be recorded
and indexed. A BTR % value at time "j" may be represented as BTR %
[j] and a BTR % value at time "n" may be represented as BTR % [n].
In this formula, an input may be determined by finding the current
BTR % value, represented as BTR % [n], subtracting a difference
between the current and a prior BTR % value, and dividing the
result by the sample index. In an exemplary embodiment, Applicants
chose to sample the BTR % once per second so that BTR % [j] was the
BTR % value obtained 10 samples before the most current sample was
taken. Other samples and comparisons may be envisioned and utilized
without departing from the spirit of the inventions disclosed
herein.
FIG. 17 illustrates a chart of various data collected from sensors
during the freeze cycle of an exemplary dispensing system in
accordance with certain teachings of the present disclosure.
Represented in this are the low side pressure 1710, the return
pressure 1712, the superheat 1714, they duty cycle 1716 and the BTR
% 1722. Calculations are made from samples of the BTR % 1722 to
find an input as described. In FIG. 17, the input is shown as a BTR
Rate 1718, which is not shown to scale. At each 10 samples in this
figure, a target 1720 is calculated. This input is then used to
control the duty cycle of the refrigeration system. Successive
values of "Input" will result in different duty cycles used in the
freezing process until the desired BTR % value is attained. As may
be understood by those of ordinary skill in the art, the BTR % 1722
shows a desirable freezing rate.
As may be appreciated by those skilled in the art, other algorithms
may be used to determine an input to the controller. As one of many
examples of this, the index of previous samples may be
exponentially decayed as opposed to sequentially decreased.
FIG. 12 illustrates a block diagram of beater load rate controller
in accordance with certain teachings of the present disclosure.
Process 1200 contains a PID controller 1210, and a processor 1220.
Various inputs are sent to the PID 1210. The PID 1210 sends the PID
output 1258 to the processor 1220. The processor controls various
functions of the food dispensing system such as the refrigeration
duty cycle. The PID 1210 may also receive other inputs such as the
Beater Load Rate of Change (ROC) 1254 and a Target Beater Load ROC
1252. In one embodiment, the Beater Load ROC 1254 and the Target
Load Beater ROC may be compared by another process 1250 prior to
being sent to the PID 1210.
As was noted previously, the viscosity measurement in a frozen
beverage/dessert dispenser may be done measuring the beater motor
load. These exemplary methods and systems may build upon the
inventions disclosed herein, in which the refrigeration control,
and other controls, are achieved solely using the beater motor load
rate of change which is advantageous for controlling the process
without additional refrigeration sensors. However, the rate of
freezing can be increased in some cases by raising the duty cycle
while in other cases by lowering the duty cycle. This non-linear
behavior may be due to there being an imbalance between mass-flow
of refrigerant versus the temperature of the refrigerant. As such,
the performance of a controller using beater load Rate of Change
("ROC") may become unstable. However, due to a non-linear
correlation between duty cycle and rate of freezing, improvements
are required as a PID is not well suited for non-linear
applications. The inventions disclosed herein further stabilizes
the controller by accounting for this non-linearity. This may be
achieved using the duty cycle as feedback for PID gain
scheduling.
In a frozen product dispenser (soft serve, frozen yogurt,
milkshakes, smoothies, beverages, etc.), a refrigeration system
typically uses a metering device with some control mechanism or
algorithm. Typically, a parameter such as superheat is used to
control this metering device. This invention includes the control
of the metering device using the rate at which the product is
freezing through measuring the load of the beater motor.
PID gain scheduling may correct the weaknesses of PID when applied
to non-linear systems. This exemplary method uses the duty cycle to
the refrigeration's metering valve as feedback, which becomes an
input to the PID gain scheduler.
One embodiment of this exemplary method uses hysteresis for gain
scheduling. By accounting for where the duty cycle has been
previously, the PID gains can be set such that it accounts for the
state of the system and knows whether to increase mass flow or
decrease temperature by raising or lowering the duty cycle. FIG. 10
illustrates a control block diagram of an exemplary method of duty
cycle hysteresis gain scheduling in accordance with certain
teachings of the present invention. Since PIDs are usually applied
to linear systems, they may not always perform optimally within
non-linear systems. To address this, Applicants have found that
some other sensor measures, accumulated and utilized over time, may
be used as inputs to the gain scheduler. One embodiment of the
inventions disclosed herein may be to use the duty cycle of the
refrigeration's metering valve as feedback.
Process 1000 contains a PID controller 1010, and a processor 1020.
Various inputs are sent to the PID 1010. The PID 1010 sends the PID
output 1058 to the processor 1020. The processor controls various
functions of the food dispensing system such as the refrigeration
duty cycle. Applicants have configured the processor 1020 to send
information such as the PWM valve duty cycle 1034 to a hysteresis
gain scheduler 1030. The hysteresis processor 1030 may perform
comparisons of past duty cycle readings and relay those as PID
Gains 1032 back to the PID 1010. The PID 1010 may also receive
other inputs such as the Beater Load Rate of Change (ROC) 1054 and
a Target Beater Load ROC 1052. In one embodiment, the Beater Load
ROC 1054 and the Target Load Beater ROC may be compared by another
process 1050 prior to being sent to the PID 1010.
FIG. 11 illustrates an example of the block diagram of an exemplary
method of duty cycle hysteresis gain scheduling in accordance with
certain teachings of the present disclosure. This may be utilized
as the hysteresis gain scheduler 1030 as was illustrated in FIG.
10. The method shown in FIG. 11 uses the PWM valve duty cycle 1110
as input to a gain scheduler to correct the PID control output. The
duty cycle curve 1110 is arbitrary and the rate of change
exaggerated to demonstrate the hysteresis gain scheduling control.
A high duty cycle trigger 1120 is established as well as a low duty
cycle trigger 1130. Initially, the PID gains are such that the duty
cycle and Beater Load Rate of Change (ROC) are directly
proportional. Once the high duty cycle trigger point 1150 is
reached, the PID gains are switched so that they are inversely
proportional to the Beater Load ROC. At this point, if the rate
needs to change, the duty cycle will be adjusted higher or lower.
This logic applies to the lower duty cycle trigger level 1160 as
well, where the PID gains are switched again.
Applicants have also found that fuzzy rules may be utilized to
control various processes in a frozen food dispensing unit. FIG. 13
illustrates an example of a fuzzy rule set using low, nominal and
high rules associated with the duty cycle wherein each have PID
gains associated with them. The low, nominal and high thresholds
may be empirically derived. It should be noted that while three
rules are illustrated here, any number of rules may be used in
accordance with the teachings disclosed herein.
A defuzzification algorithm may be applied to get the final
controller output. Each rule calculates the PID output with its
gains. The refrigeration duty cycle is used determined to what
degree it is low, nominal or high. This percentage is applied to
that fuzzy rule's PID output and the mean of these weighted outputs
is calculated to get the final controller output. This is shown in
the following equation which assumes the duty cycle is half way
between low and nominal:
.times..times..times..times..times..times..times..times..times..times..ti-
mes..times..times..times..times..times..times..times..times..times..times.-
.times..times..times. ##EQU00001## FIG. 14 illustrates a block
diagram of an exemplary method of utilizing fuzzy logic in
accordance with certain teachings of the present disclosure.
Process 1400, like some other processes described herein, may
compare and combine 1450 the inputs of the Target Beater Load ROC
1452 with the Beater Load ROC 144 and use that as input 1456 to a
PID controller or PID controllers with different control
algorithms. In process 1400, three (3) PID controllers are show: a
PID controller with a high rule gain scheduling 1414, a PID
controller with a nominal rule gain scheduling 1412, and a PID
controller with a low rule gain scheduling 1416. Each of these
provides their input to a defuzzification module 1470. The
defuzzification module 1470 also has a PWM Valve Duty Cycle input
1434 from the processor 1420. The defuzzification module 1470
evaluates these inputs as described previously and provides input
1458 to the processor 1420.
Applicants have further created improved methods and apparatuses
for controlling the refrigeration by using the beater load rate of
change to control the refrigeration through the use of a cascaded
controller. Viscosity measurement in a frozen beverage/desert
dispenser is commonly achieved by measuring the beater motor load.
These methods and apparatuses build upon other methods and
apparatuses taught in this disclosure in which the refrigeration
expansion valve control is achieved solely using the beater motor
load rate of change. As was noted before, due to a non-linear
correlation between the expansion valve duty cycle and rate of
freezing, improvements are required as PID is not well suited for
non-linear applications. These methods and apparatuses stabilize
the controller by utilizing a nested refrigeration controller,
which uses a linear parameter.
In accordance with certain teachings disclosed herein, a cascaded
PID control is utilized to stabilize the freezing process. The
beater load ROC controller adjusts the set point of a nested
controller as opposed to controlling the expansion valve directly.
This internal controller may be a superheat or low side pressure
controller. FIGS. 15 and 16 show two examples.
FIG. 15 illustrates a control block diagram of an exemplary method
of cascaded PID control using superheat in accordance with certain
teachings of the present disclosure. In process 1500, the beater
load ROC set point 1556 becomes an input to the nested superheat
controller 1515. The superheat then achieves its target, which may
directly correlate to the rate at which the product is freezing.
This affects the beater load Rate of Change 1560, which is fed back
to the input 1554 of the superheat controller 1515. This results in
the superheat controller 1515 having much greater stability and a
smaller time constant. The beater load ROC controller 1520 has a
significantly longer time constant and so each PID controller 1510
has its own different gains. Process 1500 also contains a
comparator 1450, the Target Beater Load ROC input 1452; the Beater
Load ROC 1454; input to the PID 1556; and a superheat comparator
1580, taking input 1555 from the processor about the superheat, and
the superheat setpoint 1559.
FIG. 16 illustrates a control block diagram of an exemplary method
of cascaded PID control using low side pressure in accordance with
certain teachings of the present disclosure. In process 1600, the
beater load ROC set point 1656 becomes an input to the nested low
side pressure controller 1615. The low side pressure then achieves
its target, which may directly correlate to the rate at which the
product is freezing. This affects the beater load Rate of Change
1660, which is fed back to the input 1654 of the low side pressure
controller 1615. This results in the low side pressure controller
1615 having much greater stability and a smaller time constant. The
beater load ROC controller 1620 has a significantly longer time
constant and so each PID controller 1610 has its own different
gains. Process 1600 also contains a comparator 1650, the Target
Beater Load ROC input 1652; the Beater Load ROC 1654; input to the
PID 1656; and a low side pressure comparator 1680, taking input
1655 from the processor about the low side pressure, and the low
side pressure setpoint 1659.
These exemplary methods offer improved stability for controlling
frozen dessert and beverage characteristics. These exemplary
methods improve instability of PID control due to system
non-linearity when used to control beater load ROC via a
refrigeration expansion valve.
Other and further embodiments utilizing one or more aspects of the
inventions described above can be devised without departing from
the spirit of Applicant's invention. For example, one or more of
the exemplary methods and apparatuses disclosed herein may be
combined with each other or with previously known methods and
apparatuses to control the refrigeration of a frozen beverage
machine. Further, the various methods and embodiments of the
methods of manufacture and assembly of the system, as well as
location specifications, can be included in combination with each
other to produce variations of the disclosed methods and
embodiments. Discussion of singular elements can include plural
elements and vice-versa.
The order of steps can occur in a variety of sequences unless
otherwise specifically limited. The various steps described herein
can be combined with other steps, interlineated with the stated
steps, and/or split into multiple steps. Similarly, elements have
been described functionally and can be embodied as separate
components or can be combined into components having multiple
functions.
The inventions have been described in the context of preferred and
other embodiments and not every embodiment of the invention has
been described. Obvious modifications and alterations to the
described embodiments are available to those of ordinary skill in
the art. The disclosed and undisclosed embodiments are not intended
to limit or restrict the scope or applicability of the invention
conceived of by the Applicants, but rather, in conformity with the
patent laws, Applicants intend to fully protect all such
modifications and improvements that come within the scope or range
of equivalent of the following claims.
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